1,802 research outputs found

    Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results

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    The Binary Population and Spectral Synthesis (BPASS) suite of binary stellar evolution models and synthetic stellar populations provides a framework for the physically motivated analysis of both the integrated light from distant stellar populations and the detailed properties of those nearby. We present a new version 2.1 data release of these models, detailing the methodology by which BPASS incorporates binary mass transfer and its effect on stellar evolution pathways, as well as the construction of simple stellar populations. We demonstrate key tests of the latest BPASS model suite demonstrating its ability to reproduce the colours and derived properties of resolved stellar populations, including well- constrained eclipsing binaries. We consider observational constraints on the ratio of massive star types and the distribution of stellar remnant masses. We describe the identification of supernova progenitors in our models, and demonstrate a good agreement to the properties of observed progenitors. We also test our models against photometric and spectroscopic observations of unresolved stellar populations, both in the local and distant Universe, finding that binary models provide a self-consistent explanation for observed galaxy properties across a broad redshift range. Finally, we carefully describe the limitations of our models, and areas where we expect to see significant improvement in future versions.Comment: 69 pages, 45 figures. Accepted for publication in PASA. Accompanied by a full, documented data release at http://bpass.auckland.ac.nz and http://warwick.ac.uk/bpas

    How pragmatic are the randomised trials used in recommendations for control of glycosylated haemoglobin levels in type 2 diabetic patients in general practice: an application of the PRECIS II tool.

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    BACKGROUND: Recommendations for good clinical practice have been reported to be difficult to apply in real life by primary care clinicians. This could be because the clinical trials at the origin of the guidelines are based on explanatory trials, conducted under ideal conditions not reflecting the reality of primary care, rather than pragmatic trials conducted under real-life conditions. The objective of this study was to evaluate how pragmatic are the clinical trials used to build the French High Authority of Health's recommendations on the management of type II diabetes. METHODS: Trials from the 2013 Cochrane meta-analysis that led to the 2013 French High Authority of Health's recommendations on the management of type II diabetes were selected. Each trial was analysed by applying the PRECIS-2 tool to evaluate whether the trial was pragmatic or explanatory, according to the nine domains of PRECIS-2. Each domain was scored between 1 (very explanatory) and 5 (very pragmatic) by two blinded researchers, and consensus was reached with a third researcher in case of discrepancy. Median scores were calculated for each of the nine domains. RESULTS: Twenty-three articles were analysed. Eight out of nine domains - namely eligibility, recruitment, setting, organisation, flexibility of delivery, flexibility of adherence, follow-up, and primary outcome - had a median score of less than 3, indicating a more explanatory design. Only the primary analysis domain had a score indicating a more pragmatic approach (median score of 4). In more than 25% of the articles, data to score the domains of recruitment, flexibility of delivery, flexibility of adherence, and primary analysis were missing. CONCLUSIONS: Trials used to build French recommendations for good clinical practice for the management of type 2 diabetes in primary care were more explanatory than pragmatic. Policy-makers should encourage the funding of pragmatic trials to evaluate the different strategies proposed for managing the patient's treatment according to HbA1C levels and give clinicians feasible recommendations

    Polariton Condensate Transistor Switch

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    A polariton condensate transistor switch is realized through optical excitation of a microcavity ridge with two beams. The ballistically ejected polaritons from a condensate formed at the source are gated using the 20 times weaker second beam to switch on and off the flux of polaritons. In the absence of the gate beam the small built-in detuning creates potential landscape in which ejected polaritons are channelled toward the end of the ridge where they condense. The low loss photon-like propagation combined with strong nonlinearities associated with their excitonic component makes polariton based transistors particularly attractive for the implementation of all-optical integrated circuits

    Temperature mapping above and below air film-cooled thermal barrier coatings using phosphor thermometry

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    Thermal barrier coatings (TBCs) are typically used in conjunction with air film cooling to maximize overall cooling effectiveness and reliability while minimizing sacrifices in engine performance. The effects of thermal barrier coating (TBC) thermal protection and air film cooling effectiveness have usually been studied separately; however, their contributions to combined cooling effectiveness are interdependent and are not simply additive. The combined cooling effectiveness is always less than the sum of the cooling effectiveness of stand-alone TBC protection and stand-alone air film cooling. These diminishing returns arise because adding the thermally insulating TBC between the cooling air and the surface to be cooled reduces the air film cooling effectiveness and because the air film cooling reduces the heat flux through the TBC and therefore reduces the temperature difference sustained across the TBC thickness. Due to these considerations, combined cooling effectiveness must be measured to achieve an optimum balance between TBC thermal protection and air film cooling. In this investigation, temperature mapping above and below air film-cooled TBCs was performed using luminescence lifetime imaging-based phosphor thermometry. Measurements were performed in the NASA GRC Mach 0.3 burner rig on a TBC-coated plate using a scaled-up cooling hole geometry where both the hot mainstream gas temperature and the blowing ratio were varied. Surface temperature maps were obtained from a Cr-doped GdAlO3 thermographic phosphor deposited on the surface of the electron-beam vapor-deposited yttria-stabilized zirconia (YSZ) TBC. From separate plates, temperature maps from the bottom of the TBC were obtained from a thin Er-doped YSZ layer integrated into the TBC below the overlying undoped YSZ. Procedures for temperature and cooling effectiveness mapping above and below the air film-cooled TBC surface are described. Most importantly, these measurements enable mapping the combined cooling effectiveness below the TBC, which is more important than surface cooling effectiveness when there is a barrier coating between the hot mainstream gas and the surface that needs thermal protection. Advantages of the luminescence lifetime imaging method over infrared thermography, as well as its limitations to steady-state conditions are discussed

    Can lay health workers support the management of hypertension? Findings of a cluster randomised trial in South Africa.

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    Introduction: In low/middle-income countries with substantial HIV and tuberculosis epidemics, health services often neglect other highly prevalent chronic conditions, such as hypertension, which as a result are poorly managed. This paper reports on a study to assess the effect on hypertension management of lay health workers (LHW) working in South African rural primary healthcare clinics to support the provision of integrated chronic care. Methods: A pragmatic cluster randomised trial with a process evaluation in eight rural clinics assessed the effect of adding two LHWs supporting nurses in providing chronic disease care in each intervention clinic over 18 months. Control clinics continued with usual care. The main outcome measure was the change in the difference of percentage of clinic users who had elevated cardiovascular risk associated with high blood pressure (BP) before and after the intervention, as measured by two cross-sectional population surveys. Results: There was no improvement in BP control among users of intervention clinics as compared with control clinics. However, the LHWs improved clinic functioning, including overall attendance, and attendance on the correct day. All clinics faced numerous challenges, including rapidly increasing number of users of chronic care, unreliable BP machines and cuffs, intermittent drug shortages and insufficient space. Conclusion: LHWs improved the process of providing care but improved BP control required improved clinical care by nurses which was compromised by large and increasing numbers of patients, the dominance of the vertically funded HIV programme and the poor standards of equipment in clinics. Trial registration number: ISRCTN12128227.The Nkateko study was funded by the UK Medical Research Council under the Global Alliance for Chronic Diseases (GACD) Programme

    Evolution and Nucleosynthesis of Very Massive Stars

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    In this chapter, after a brief introduction and overview of stellar evolution, we discuss the evolution and nucleosynthesis of very massive stars (VMS: M>100 solar masses) in the context of recent stellar evolution model calculations. This chapter covers the following aspects: general properties, evolution of surface properties, late central evolution, and nucleosynthesis including their dependence on metallicity, mass loss and rotation. Since very massive stars have very large convective cores during the main-sequence phase, their evolution is not so much affected by rotational mixing, but more by mass loss through stellar winds. Their evolution is never far from a homogeneous evolution even without rotational mixing. All VMS at metallicities close to solar end their life as WC(-WO) type Wolf-Rayet stars. Due to very important mass loss through stellar winds, these stars may have luminosities during the advanced phases of their evolution similar to stars with initial masses between 60 and 120 solar masses. A distinctive feature which may be used to disentangle Wolf-Rayet stars originating from VMS from those originating from lower initial masses is the enhanced abundances of neon and magnesium at the surface of WC stars. At solar metallicity, mass loss is so strong that even if a star is born with several hundred solar masses, it will end its life with less than 50 solar masses (using current mass loss prescriptions). At the metallicity of the LMC and lower, on the other hand, mass loss is weaker and might enable star to undergo pair-instability supernovae.Comment: 42 pages, 20 figures, Book Chapter in "Very Massive Stars in the Local Universe", Springer, Ed. Jorick S. Vin

    A structural role for arginine in proteins: Multiple hydrogen bonds to backbone carbonyl oxygens

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    We propose that arginine side chains often play a previously unappreciated general structural role in the maintenance of tertiary structure in proteins, wherein the positively charged guanidinium group forms multiple hydrogen bonds to backbone carbonyl oxygens. Using as a criterion for a “structural” arginine one that forms 4 or more hydrogen bonds to 3 or more backbone carbonyl oxygens, we have used molecular graphics to locate arginines of interest in 4 proteins: Arg 180 in Thermus thermophilus manganese superoxide dismutase, Arg 254 in human carbonic anhydrase II, Arg 31 in Streptomyces rubiginosus xylose isomerase, and Arg 313 in Rhodospirillum rubrum ribulose‐1,5‐bisphosphate carboxylase/oxygenase. Arg 180 helps to mold the active site channel of superoxide dismutase, whereas in each of the other enzymes the structural arginine is buried in the “mantle” (i.e., inside, but near the surface) of the protein interior well removed from the active site, where it makes 5 hydrogen bonds to 4 backbone carbonyl oxygens. Using a more relaxed criterion of 3 or more hydrogen bonds to 2 or more backbone carbonyl oxygens, arginines that play a potentially important structural role were found in yeast enolase, Bacillus stearothermophilus glyceraldehyde‐3‐phosphate dehydrogenase, bacteriophage T4 and human lysozymes, Enteromorpha prolifera plastocyanin, HIV‐1 protease, Trypanosoma brucei brucei and yeast triosephosphate isomerases, and Escherichia coli trp aporepressor (but not trp repressor or the trp repressor/operator complex). In addition to helping form the active site funnel in superoxide dismutase, the structural arginines found in this study play such diverse roles as stapling together 3 strands of backbone from different regions of the primary sequence, and tying α‐helix to α‐helix, ÎČturn to ÎČ‐turn, and subunit to subunit. Copyright © 1994 The Protein Societ

    Temperature Mapping at the Thermal Barrier Coating/Bond Coat Interface by Luminescence Lifetime Imaging Using Integrated Erbium-Doped Sublayers

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    Full-field temperature mapping of thermal barrier coated components by either infrared thermography or phosphor thermometry has been limited to surface temperature mapping even though temperature mapping at the thermal barrier coating (TBC)/bond coat interface is more relevant for evaluating the TBC thermal protection performance. For the first time, 2D temperature mapping at the TBC/bond coat interface has now been achieved by full-field luminescence lifetime imaging measurements of emission from a thin erbium-doped yttria-stabilized zirconia (YSZ) sensing layer integrated into the TBC below the overlying undoped YSZ. This new capability was applied to map temperatures at the TBC/bond coat interface for TBC-coated specimens subjected to a heat flux produced by the NASA Glenn high heat flux laser facility. In particular, thermal gradients at the TBC/bond coat interface were mapped in regions where the TBC was subjected to erosion or to mechanically induced delamination crack propagation. Finally, temperature mapping of the TBC/bond coat interface was used to evaluate the effectiveness of surface air film cooling at the TBC/bond coat interface
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